1. Field of the Invention
The present invention relates to a machine for tamping ballast under a track and movable in an operating direction, which comprises an elongated machine frame extending along the track in a longitudinal direction, a tool carrier frame supporting a ballast tamping head and a track lifting and lining unit, a displacement drive connecting the tool carrier frame to the machine frame for displacing the tool carrier frame relative to the machine frame in the longitudinal direction, and at least one undercarriage supporting each frame on the track.
2. Description of the Prior Art
Such a machine has been disclosed, for example, in U.S. Pat. No. 5,133,263. The elongated machine frame forming a bridge over the tool carrier frame moves continuously along the track during operation while the tool carrier frame moves intermittently between successive tamping stages. This machine is very efficient in tamping tangent track but cannot be used in switch sections.
Another type of continuously operating tamping machine capable of tamping two adjacent ties simultaneously is described in U.S. Pat. No. 4,928,599, but this machine, too, cannot operate in switches.
While U.S. Pat. No. 4,627,360 describes a continuously operating tamping machine with a longitudinally displaceable tool carrier frame equipped with special tamping, lifting and lining tools capable of use in switches, no such machine has been built for commercial use.
U.S. Pat. No. 4,825,768 discloses a mobile machine for leveling, lining and tamping a track switch. However, the tamping head and track lifting and lining unit are mounted on the machine frame of this machine and not on a longitudinally displaceable tool carrier frame. The machine runs on a main track and, for synchronously lifting an outer rail of a branch track in a switch section, the machine frame supports an auxiliary rail lifting device. This device is telescopingly extensible in a transverse direction for engagement with the outer branch track rail and comprises a carrier for a rail clamping element and flanged wheel associated therewith, the carrier being attached to the machine frame by a cable. In this way, the clamping element and cooperating flanged wheel can be transversely and vertically adjusted for gripping engagement with the outer branch track rail. The lifted outer branch track rail is then tamped by an auxiliary tamping unit so that the asymmetrical switch section is properly tamped along its long ties in an accurately leveled position.